[en] The sintering of metal injection moulded stainless steel was investigated using in situ neutron diffraction with different sintering temperatures, from 1270 deg. C up to 1390 deg. C, with sintering profiles that were based on those used in industry. The production of an unwanted high temperature phase, δ-ferrite, was observed during sintering and is seen to be retained in the final product after sintering. Ferrite production during sintering acts to speed up the sintering process by forming in the grain pores but is unwanted in the final product as it is a soft and malleable phase. The ferrite that was formed at high temperature was observed to not completely disappear during cooling as a result of the coexistence of dual high temperature phases delta-ferrite and gamma-austenite during the high temperature soak. This suggests the segregation of the alloying elements between the two phase which changes the composition of the phase grains and allows the ferrite to exist during cooling, resulting in the unwanted phase in the final product.

[en] Abstract only

[en] Wombat was originally conceived as a high speed powder diffractometer, and during its operational life so far has performed this role admirably. However, when it was determined that the detector to be procured would have full two-dimensional resolving capability, it was clear that the instrument would be useful for a number of measurement techniques other than standard powder diffraction. This presentation will review experiments that have been successfully performed on Wombat and published in the domains of texture, single crystal (both chemical and magnetic structure) and diffuse scattering.

[en] Full text: A neutron reflectometer is one of the initial suite of neutron scattering instruments to be constructed on the replacement reactor for HIFAR. There is strong support for such an instrument from the Australian neutron user community. Currently Australians requiring such an instrument work at overseas facilities, as there are no such instruments on HIFAR. A project has recently commenced to construct a reflectometer on HIFAR to gain experience in this technique with a view to future development of a world class reflectometer at the new facility and to begin to address the needs of the Australian scientific community and industry. The HIFAR reflectometer will also serve the vital need to develop expertise in this area for AINSE members as well as ANSTO staff. This presentation will give details of the scope of the project, the design of the proposed instrument and some envisaged uses upon its completion

[en] Full text: In this paper we will discuss the magnetic properties of the pyrochlore Nd₂Sn₂O₇ as measured with the neutron scattering instruments Wombat and Taipan at the Bragg Institute neutron scattering facility. The measurements were conducted on a polycrystalline sample in zero magnetic field and 10 Tesla. The sample, loaded in OFHC copper can, was mounted into a dilution insert and measured between 340 mK and 50 K. The results indicated that the material doesn’t spontaneously magnetically order. However, upon application of the magnetic field, the sample is easily polarised. Achieving ultra-low temperature with a powder samples is a difficult task. Here we will discuss common strategies used to improve conductivity in the mK range and the implication for this particular study. The equipment available at the neutron scattering instruments of Bragg Institute for measurements in high magnetic fields and low temperature will be also illustrated. (author)

[en] The susceptibility of four MAX phases (Ti₂AlC, Cr₂AlC, Ti₃AlC₂, and Ti₃SiC₂) to high-temperature thermal dissociation in vacuum has been investigated using in-situ neutron diffraction. In high vacuum, these phases decomposed above 1400⁰C through the sublimation of M and A elements, forming a surface coating of MC. The apparent activation energies for the decomposition of sintered Ti₃SiC₂, Ti₃AlC₂, and Ti₂AlC were determined to be 179.3, -71.9, and 85.7 kJ mol^-1, respectively. The spontaneous release of Ti₂AlC and TiC from de-intercalation during decomposition of Ti₃AlC₂ resulted in a negative activation energy.

[en] Published in summary form only

[en] Ocean-atmosphere 14C disequilibria of the surface and deep ocean reflect past changes in the efficiency of ocean-atmosphere CO2 exchange and ocean mixing, while it may also be related to variations in global-ocean respired carbon content. A full assessment of the oceanic mechanisms controlling deglacial changes in atmospheric CO2 is complicated by a lack of high-resolution 14C ventilation age estimates from the Southern Ocean and other key regions due to low foraminiferal abundances in marine sediments in those areas. Here we present high-resolution deglacial 14C ventilation age records from key sites in the Atlantic and Indian Sector of the Southern Ocean obtained by radiocarbon analyses of small benthic and planktic foraminiferal samples (<1 mg CaCO3) with the UniBe Mini-Carbon Dating System (MICADAS). Our analyses specifically circumvent foraminiferal sample size requirements related to “conventional” accelerator mass spectrometer analyses involving sample graphitization (>1 mg CaCO3 in most laboratories). Complementing multi-proxy analyses of sea surface temperature (SST) changes at these sites allow the construction of a radiocarbon-independent age model through a stratigraphic alignment of SST changes to Antarctic (ice core) temperature variations. We demonstrate the value of refining the age models of our study cores on the basis of high-resolution sedimentary U- and Th flux estimates, which allows an improved quantification of surface ocean reservoir age variations in the past. The resulting deep-ocean ventilation age changes are compared against qualitative and quantitative indicators of bottom water [O2] variations, in order to assess the role of Southern Ocean overturning dynamics in respired carbon changes at our study sites. We discuss the implications of our new radiocarbon- and bottom water [O2] data for the ocean’s role in atmospheric CO2 changes throughout the last deglaciation, and evaluate down-stream effects of southern high-latitude surface ocean reservoir age anomalies.

[en] Full text: Polarised neutron scattering has been used extensively to study magnetism in materials. Diffraction allows us to resolve the distribution and orientation of the magnetic moments down to the atomic scale. Inelastic scattering studies the magnetic excitations. The complex magnetic structure in magnetic nanoparticles is a hot topic for Small Angle Neutron Scattering (SANS). Novel magnetic thin film and multilayer are the subjects of neutron reflectometry. The technique is also increasingly being used to significantly enhance the signal-to-noise ratio in SANS measurement of hydrogen-rich materials. At ANSTO, polarised neutron option is currently available on both the SANS instrument “Quokka” (incident beam) and the reflectometer “Platypus” (incident and scattered beam). Recent technological advance of polarised Helium-3 based neutron spin-filter technique has opened up the possibility of using polarised neutrons on a wider range of instruments. In addition to enhancing the capabilities of Quokka (both incident and scattered beam for hydrogen-rich material and magnetic nanoparticle studies) and Platypus (wide-angle analysis for e.g. patterned magnetic surface structure), we are installing and testing polarised neutron equipment on the diffractometer “Wombat” and inelastic-scattering instruments “Taipan”, “Pelican” and “Sika”. This new capability will become available for experiments from July 2014. Furthermore, a new supermirror polariser is being commissioned on Pelican for polarised inelastic scattering work. In this presentation, examples illustrating the technique and use of polarised neutron scattering and the current status of installation and test on instruments will be provided. (author)

[en] A pilot experiment was performed using the WOMBAT powder diffraction instrument at ANSTO in which the first neutron diffraction peak (Q_0) was measured for D_20 flowing in a 2 mm internal diameter aluminium tube. Measurements of Q_0 were made at -9, 4.3, 6.9, 12, 18.2 and 21.5 °C. The D_20 was circulated using a siphon with water in the lower reservoir returned to the upper reservoir using a small pump. This enabled stable flow to be maintained for several hours. For example, if the pump flow increased slightly, the upper reservoir level rose, increasing the siphon flow until it matched the return flow. A neutron wavelength of 2.4 Å was used and data integrated over 60 minutes for each temperature. A jet of nitrogen from a liquid N_2 Dewar was directed over the aluminium tube to vary water temperature. After collection of the data, the d spacing of the aluminium peaks was used to calculate the temperature of the aluminium within the neutron beam and therefore was considered to be an accurate measure of water temperature within the beam. Sigmaplot version 12.3 was used to fit a Weibull five parameter peak fit to the first neutron diffraction peak. The values of Q0 obtained in this experiment showed an increase with temperature consistent with data in the literature but were consistently higher than published values for bulk D_20. For example at 21.5 °C we obtained a value of 2.008 Å-1 for Q0 compared to a literature value of 1.988 A"-"1 for bulk D_20 at 20 °C, a difference of 1%. Further experiments are required to see if this difference is real or artifactual.